Less than nine months after the repeal of "don't ask don't tell", the US military has announced that it will participate in this month's celebration of gay pride.

The Pentagon is to organise the first official event to recognise gay and lesbian troops. The move, first reported by Associated Press, was heralded by lesbian and gay groups as a sign of how quickly the military has acted to open up the services in the wake of the repeal.

"This is a tremendous accomplishment to be happening not one year since the repeal of don't ask, don't tell," said Josh Seefried, an air force lieutenant with the Joint Base Maguire-Dix-Lakehurst in New Jersey.

Seefried made a comparison with the British military services, where despite the lifting of a ban on gays in the military ten years ago, it took some time for gay service personnel to be open about their sexuality. "Here, on day one we had more than 100 come out in all branches of the military," he said.

The Pentagon has declined to give details of the event that it will organise as part of pride month. But it is certain to involve the saluting of gay and lesbian troops, in an echo of how African American and other ethnic groups are celebrated at different times in the annual calendar.

The event will be the latest in the rolling out of the new tolerance within the military. Don't ask, don't tell, which was introduced under President Clinton in 1993, forced the discharge of more than 13,000 men and women sacked for revealing their sexual orientation.

The impressively rapid shift in culture has been evident in other ways. OutServe, the association of actively serving LGBT military personnel in which Seefried is a co-director, has grown rapidly since the repeal last September.

Under DADT, OutServe had about 1,700 members all of whom were taking a risk by attaching their names to the group. Now membership has grown to 5,700.